Recently, high function skin cosmetics having humectant actions, whitening actions, antioxidation actions, etc. are desired and the development thereof is desired. Therefore, for emulsified compositions which constitute skin cosmetics, for the purpose of manifesting the target high function, pH adjustment, thickening, etc., there are many cases where electrolytes such as plant extracts, organic acids and salts thereof including citric acid, ascorbic acid, and 4-methoxysalycilic acid are blended in as salt type drugs.
However, there is an essential problem with emulsified compositions in that the addition of an electrolyte decreases their stability over time and over varying temperatures. Particularly, the stability of low-viscosity oil-in-water emulsified compositions having aqueous solution-like physical properties dramatically worsens with the addition of a salt type drug consisting of electrolytes.
Such destabilization of emulsified compositions by the addition of electrolytes is also described in Patent Document 1, Non-Patent Document 1, Non-Patent Document 2, etc.
On the other hand, as examples of oil-in-water emulsified compositions prepared by miniaturizing emulsified particles by means of high pressure emulsification, Patent Documents 2-4 disclose oil-in-water emulsified compositions having aqueous solution-like low viscosity physical properties and also a cream-like texture during use. Patent Documents 2 and 3 are basically technologies using higher fatty acid soaps and Patent Document 4 is basically a technology using N-long chain acyl acidic amino acid mono salts.
However, the oil-in-water emulsified compositions of Patent Documents 2-4 have a relatively narrow range of selection in terms of combinations of surfactants and oil components as well as their blend ratios that can provide stable emulsified compositions. Therefore, it is not necessarily easy to stabilize said emulsified compositions when desired amounts of various salt type drugs are blended in: in many cases it is with difficulty.